1. Field of the Invention
This invention relates generally to the field of protective coatings for use with structural members and more particularly to encapsulation of portions or the entirety of structural members utilized in structures for outdoor use including playground equipment.
2. Description of the Related Art
The use of wood-based columns and beams as structural supports for outdoor equipment including playground equipment and the like is well known. The usual materials of construction for such outdoor structures are wood or a combination or composite of wood or other materials. Playground equipment constructed with wood and wood product structural members and accessories are necessarily located in outdoor and environmentally hostile environments, subjected not only to wide variations in humidity but also ground moisture, wide-ranging variations in temperature, as well as exposure to vermin, pests, animals and their by-products, as well as chaffing and impact caused by use of that equipment or maintenance and gardening equipment used in the immediate area. Such structural materials may also be damaged or subject to deterioration by salt water, corrosive pollution, cycles of wetting and drying, cycles of freezing and thawing and electrolysis in coastal or marine environments. Thus, erosion, marine organisms, mechanical impact, water content and abrasion may also cause premature wear and failures of even properly designed structures. Moreover, incomplete protection of the wooden structural member will allow moisture to seep into the structural member or fasteners connected therethrough, causing the fastener to rust or corrode and allowing mildew to form around the fastener. Moisture also causes galvanic action between dissimilar metals such as support brackets and fasteners often used in outdoor equipment which leads to corrosion. In turn, such deterioration will compromise the structural integrity of surrounding and supporting materials, including the wooden substrate.
Protecting wood-based supports, columns or other load supporting structural members used in such hostile environments is often times unreliable and inconsistent in the desired protective effects. Some known alternatives or methods for minimizing or arresting deterioration include pressurized, chemically-impregnated wood treatments, and protective coatings include vinyl wraps. However, those approaches have been known to provide inconsistent results. Furthermore, such means of repair or protection are only short term solutions and may be unfeasible for certain structures. For instance, pressure treated wooden products are susceptible to uneven processing and furthermore do not overcome the problem of splintering which is of significant importance for playground equipment, and vinyl wraps are subject to puncture and tearing from mechanical impact and heretofore have not satisfactorily addressed problems of moisture seepage at the ends and feet of components to be positioned adjacent to surface level. In addition, most protective coatings eventually fail due to inadequate surface preparation, improper application, ultra violet light exposure, mechanical wear or pinhole defects.
A known repair and protective procedure for damaged, as well as new structures for use with outdoor and corrosive environments provides for encapsulation in a corrosion resistant polymer jacket. By pouring a flowable mixed epoxy material into a surrounding form or jacket, the epoxy grout would solidify or harden about the structural component, thus providing a good seal against environmental antagonists, and also sealing off oxygen incursion to thereby prevent deterioration of the wooden structure.
An example of a protective and repair encapsulation technique is provided in U.S. Pat. No. 4,019,301 issued to Fox. While an improvement over prior practice, the Fox method can often be unreliable. By simply pouring the batch mixed epoxy encapsulating material into the surrounding form, no assurance is obtained that gravity flow will effect elimination of voids or seams by completely filling the surrounding form or that premature set up of the encapsulating material will not channel the filling material flow. Through the process of pouring the epoxy into the submerged fiberglass jacket or form, water can dilute, entrain or mix with the epoxy, thus adversely affecting the engineering properties of the protective or repair system. The pouring procedure also can create holidays or non-bonded cold joints between pours, be very time consuming, messy and impractical for structures that are not readily accessible. Furthermore, no provision was made for verifying, by visual observation or otherwise, that the encapsulating material fully filled the jacket form or for field verifying that adequate structural bonding to the structure has occurred.
In addition, it is well known that wood and wood products are susceptible to wood destroying organisms such as insects and fungi, as well as to moisture when exposed to rain, snow or substantial amounts of ambient moisture. Even when such wood and wood products are treated with preservatives such as borates and other water soluble infection controlling compositions, effective usefulness is limited because such water soluble compositions leach out of the wood, leaving it exposed to infection. Treated wood, for example, could not be left exposed to the elements in use, storage or shipment. Thus, wood could not be treated at a central location, transported to and stored in the open at a construction site.
Heretofore, conventional methods for protecting such wood and wood-based playground equipment have included pressure treatment of the timbers and connecting members from which that equipment is constructed. It is also known, and commonly recommended, to support the lower portions of the playground equipment at or several inches above ground level using a concrete pad or the like in an effort to isolate the lower portion of the wood structural member from ground moisture, ponding, and constant attack by ground-based insect and animal exposure. Also, it is known to coat such timbers and connecting members in a polymeric sheathing (as noted above) in an effort to provide an inert barrier against moisture, insects and other elements deleterious to long-term structural integrity of the structure. One prior art approach was to provide a polymeric sheathing along the longitudinal faces of the timbers, followed by the attachment of end caps. Heretofore, such efforts have exhibited important shortcomings as described, and in the instance of the prior art end caps, those articles typically include edges that are not sealed against the timbers to which they are fitted, thereby enabling the ingress of moisture and other elements in the manner described.
Accordingly, there is a need for a protective, all-encompassing coating for outdoor structures such as playground equipment subjected to harsh environmental elements and physical contact that overcomes the problem of splintering common to pressure-treated but unsheathed wooden structural members while protecting against agents that cause deterioration and premature deterioration of those structural components.